The artificial kidney was first successfully used on a patient in 1943. At that time, the machine consisted of a long tube of cellophane, a large tank of fluid called dialysate, and a very rapid blood flow from large tubes to arteries and veins. The blood flowed through the tubes of cellophane, and the dialysate around the cellophane. Impurities in the blood were removed by diffusion through the membranes, into the dialysate, a process termed "dialysis".
A typical modern version of a high flow rate dialyzer is shown by Bluemle, Jr. in U.S. Pat. No. 3,362,540. This patented construction is typical of the "cone type" dialyzers currently in use which are large (his unit is 30 inches in diameter) and typically require both semi-permeable membranes to carry out the dialysis and separator discs both to protect the membranes against rupture and also, usually, to promote turbulent flow at the membrane surface so that the dialysate solution performs with maximum efficiency to remove impurities from the blood flowing on the other side of the membrane.
Such artificial kidney machines have many inherent disadvantages to the patient. They require the patient to be immobilized for long periods of time on the order of 6 hours, 3 times per week. Because of the speed at which contaminants and water are removed from the blood, patients often suffer a decrease in blood pressure causing weakness or nausea. Another person is required to operate the machine. Some patients require 12-24 hours to recover from the procedure. During the treatment a large volume of blood (on the order of 300-500 ml) must leave the body at one time. This "priming volume" requires the use of a great amount of saline solution to prime the device which tends to dilute the patient's blood considerably and also results in some blood loss at the end of the procedure. These machines require an arterial access to the bloodstream in order to obtain an adequately high flow rate on the order of 300 ml/minute. A high flow is necessary to mix the blood near membrane surfaces and even such high flow rate is considered to need augmentation to obtain better mixing, and hence more efficient impurity exchange at the membrane surfaces. A large dialysate reservoir on the order of 100-200L is required to accomodate the required dialysate flow of 1 to 5L per minute.
Various novel configurations appear in the art, such as that shown by Heden, U.S. Pat. No. 3,352,422, for the purpose of achieving maximum mixing at the membrane surfaces.
With existing devices, patients must have either tubes extending from arteries or veins, or a subcutaneous fistula into which needles are inserted. The blood flows through a long membrane tube or parallel plates or membrane which are contacted with a fast flow of dialysate fluid. The present artificial kidneys are bulky and require much auxiliary equipment for water purification and dispensing. The treatment is usually done in a specifically equipped room. Even if the treatment is performed in the patient's home the equipment, training and hospitalization costs are approximately $15,000.00 per year. The cost is inherently high because of the complexities and problems of the present artificial kidney machines.